This invention relates generally to the field of automotive alternators, and in particular the invention relates to stator leads and terminal insulators for alternators.
Typical oil cooled alternators for heavy duty applications like busses and coaches include a stator having stator windings positioned about a rotor. The stator windings are encapsulated in an oil-proof casing that includes a rectifier housing. The stator includes terminals that extend through the rectifier housing to provide an electrical connection from the exterior of the rectifier housing to the windings on the interior of the housing.
FIG. 1 shows a perspective view of a typical oil cooled heavy duty alternator 20 having the rectifier housing removed to expose the stator windings 24. The stator windings 24 include three distinct windings that make a three-phase winding set, connected in delta or wye fashion, and positioned on a stator core. The windings 24 may be made of any of several types of windings, including hairpin-type windings and copper wound windings. Three stator leads 26 are provided in association with the windings 24. The leads 26 carry current from the three-phase windings, and the electric potential between different leads is measured as the line-to-line voltage. The leads 26 are typically flexible and comprised of stranded cable. Accordingly, the term cable leads is also used herein to refer to the stator leads. Of course, any number of other conductors could be used for the stator leads, including solid copper wire or other flexible wire types. Each lead 26 is covered with a heavy fiberglass insulating sleeve 30. The insulating sleeves 30 are used to protect the leads 26 from shorting against other stator conductors should the flexible stator leads accidentally come into contact with other conductors.
The cable leads 26 are also connected to the stator terminals 28, and provide an electric path between the terminals and the three-phase windings 24. Each terminal is made of a conductive material such as brass. When a rectifier housing is placed over the stator, the terminals extend through holes in the housing to provide a conductive path from the exterior of the alternator casing 22 to the interior of the alternator casing. Each terminal 28 is associated with a square insulator 32 positioned at its base, where the cable lead 26 connects to the terminal. Each terminal is also associated with a hat-shaped insulator having a cylindrical portion and a flared round top. This hat shaped insulator is positioned over on the terminal once the rectifier housing is placed on the alternator such that the cylindrical portion seats in the terminal holes of the rectifier housing, and the flared round top rests against the exterior of the rectifier housing. These six insulators (two for each terminal) protect the terminals from inappropriate contact with the rectifier housing.
As shown in FIG. 1, before the rectifier housing is place on the alternator, the terminals 28 are only connected to the cable leads 26, and the terminals 28 are not otherwise fixed with respect to the alternator casing 22. Of course, the cable leads 26, are flexible and do not hold the terminals 28 securely in place. Thus, before assembly, the terminals 28 move independent with respect to each other. This independent movement of each terminal 28 can cause problems during assembly because it is difficult to align the freely moving terminals 28 with the holes of the rectifier housing.
After the alternator is fully assembled and placed in operation, electric current is generated in the stator windings 24 and delivered to on-board loads. However, the significant electric currents flowing through the conductors of the alternator can generates excessive heat during alternator operation. Thus, cooling oil is provided within the alternator to dissipate the heat. The cooling oil flows between the alternator conductors, directly contacting the conductors, and drawing heat away from the conductors. Still, not all conductors of the alternator come into direct contact with the cooling oil. In particular, although the insulating sleeves 30 sufficiently protect the cable leads 26 against shorting during alternator operation, they also block the cooling oil from directly contacting the cable leads. While some cooling oil migrates into the sleeves and onto the cable leads, most of the cooling oil flows around the insulating sleeves and is prevented from directly contacting the cable leads. Because a significant amount of cooling oil does not directly contact the cable leads, they are susceptible to overheating during alternator operation. Over time, the excessive heat on the cable leads can break down the conductors and their associated insulation, resulting in improper current flow and alternator malfunction.
A one-piece stator lead and terminal insulator may be used to assist in alternator assembly and/or assist with alternator cooling. The insulator comprises an arcuate plate having a plurality of retainers positioned thereon. Each of the retainers includes a cylindrical portion that rises above the plate and includes a bore adapted to receive one of the stator terminals. When the stator terminals are inserted into the retainer bores, the terminals are positioned in an upright fashion, and properly spaced so the rectifier housing may be quickly and easily positioned upon the alternator with the terminals extending through the rectifier housing. The plate also includes guides that extend from the plate in the opposite direction of the retainers. The guides are used to properly position the cable leads of the alternator against the plate and direct the leads to the terminals. A plurality of holes are also positioned upon the plate near the guides. The holes are dimensioned to receive ties for securing the leads to the plate. The ties fit through the holes of the plate and encircle the leads, thereby fastening the leads against the plate. By securing the leads to the plate, the leads are properly positioned within the alternator, secured against the insulating plate, and prevented from inappropriate contact with other conductors within the alternator. Accordingly, no insulating sleeve is required around the lead, and cooling oil from the alternator easily flows around the leads. These and other features, aspects, and advantages of the present invention will become better understood with reference to the following description and appended claims.